Method for determining electrical conductivity of earth formations from electromagnetic induction voltage measurements

Abstract

A method of determining the conductivity of earth formations penetrated by a wellbore. The method includes inserting an induction well logging instrument into the wellbore. The instrument includes a transmitter, a source of alternating current connected to the transmitter, and a receiver. The transmitter is energized with the alternating current, voltages induced in the receiver are recorded, and area enclosed with respect to a baseline, by voltage peaks present in the recorded voltages is determined. The enclosed area corresponds to the conductivity.

What is claimed is: 
     
       1. A method of determining conductivity of earth formations penetrated by a wellbore, comprising: inserting an induction well logging instrument into said wellbore, said instrument including a transmitter a source of alternating current connected to said transmitter and a receiver;   energizing said transmitter with said alternating current;   recording voltages induced in said receiver; and   determining area enclosed with respect to a baseline by voltage peaks within said detected voltages, said area corresponding to said conductivity.   
     
     
       2. The method as defined in claim 1 wherein said alternating current comprises square waves. 
     
     
       3. The method as defined in claim 1 wherein said instrument comprises a plurality of receivers at axially spaced apart locations and said steps of recording and determining said area are performed for each of said plurality of receivers. 
     
     
       4. A method of determining conductivity of earth formations penetrated by a wellbore by analyzing voltages induced in a receiver of an induction well logging instrument inserted into said wellbore, said voltages induced as a result of energizing a transmitter on said instrument with alternating current, the method comprising: determining area enclosed with respect to a zero voltage baseline by voltage peaks within said detected voltages, said area corresponding to said conductivity.   
     
     
       5. The method as defined in claim 4 wherein said alternating current comprises square waves. 
     
     
       6. The method as defined in claim 4 wherein said instrument comprises a plurality of receivers at axially spaced apart locations and said steps of recording and determining said area are performed for each of said plurality of receivers.